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[2620:137:e000::1:20]) by mx.google.com with ESMTP id uk37-20020a170907ca2500b0088401bd5130si8989729ejc.758.2023.02.06.00.44.05; Mon, 06 Feb 2023 00:44:33 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b=huCslSgQ; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229763AbjBFIlW (ORCPT + 99 others); Mon, 6 Feb 2023 03:41:22 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229701AbjBFIlU (ORCPT ); Mon, 6 Feb 2023 03:41:20 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5D3EC1715D for ; Mon, 6 Feb 2023 00:40:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1675672829; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding; bh=eDVaZJdMGL4kVKzSO0PRgS/vEsAWvBE6o/r2igpI1bc=; b=huCslSgQmIXUDfrbcfkb3rN7qFzdILt/IT1Yy6quouzsw21eyJkVFiDsRBfzQ1KXW42rkk DdAUPV9tyE8SWWyus276qG8QhGrHbfngmM/4uliUtwpb/40OmiMrYtJwf9Bx+Y8IYM482x alMWSOScVeCxCtTl6wSfdEtsKAIu9Xk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-659-6hb2469dMb-FDzgH3OfGLw-1; Mon, 06 Feb 2023 03:40:28 -0500 X-MC-Unique: 6hb2469dMb-FDzgH3OfGLw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B8B342A59567; Mon, 6 Feb 2023 08:40:27 +0000 (UTC) Received: from MiWiFi-R3L-srv.redhat.com (ovpn-12-71.pek2.redhat.com [10.72.12.71]) by smtp.corp.redhat.com (Postfix) with ESMTP id 9D5E02166B2A; Mon, 6 Feb 2023 08:40:23 +0000 (UTC) From: Baoquan He To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, akpm@linux-foundation.org, stephen.s.brennan@oracle.com, urezki@gmail.com, lstoakes@gmail.com, error27@gmail.com, Baoquan He Subject: [PATCH v5 0/7] mm/vmalloc.c: allow vread() to read out vm_map_ram areas Date: Mon, 6 Feb 2023 16:40:13 +0800 Message-Id: <20230206084020.174506-1-bhe@redhat.com> MIME-Version: 1.0 Content-type: text/plain X-Scanned-By: MIMEDefang 3.1 on 10.11.54.6 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1757070569359274954?= X-GMAIL-MSGID: =?utf-8?q?1757070569359274954?= Problem: *** Stephen reported vread() will skip vm_map_ram areas when reading out /proc/kcore with drgn utility. Please see below link to get more details. /proc/kcore reads 0's for vmap_block https://lore.kernel.org/all/87ilk6gos2.fsf@oracle.com/T/#u Root cause: *** The normal vmalloc API uses struct vmap_area to manage the virtual kernel area allocated, and associate a vm_struct to store more information and pass out. However, area reserved through vm_map_ram() interface doesn't allocate vm_struct to associate with. So the current code in vread() will skip the vm_map_ram area through 'if (!va->vm)' conditional checking. Solution: *** To mark the area reserved through vm_map_ram() interface, add field 'flags' into struct vmap_area. Bit 0 indicates this is vm_map_ram area created through vm_map_ram() interface, bit 1 marks out the type of vm_map_ram area which makes use of vmap_block to manage split regions via vb_alloc/free(). And also add bitmap field 'used_map' into struct vmap_block to mark those further subdivided regions being used to differentiate with dirty and free regions in vmap_block. With the help of above vmap_area->flags and vmap_block->used_map, we can recognize and handle vm_map_ram areas successfully. All these are done in patch 1~3. Meanwhile, do some improvement on areas related to vm_map_ram areas in patch 4, 5. And also change area flag from VM_ALLOC to VM_IOREMAP in patch 6, 7 because this will show them as 'ioremap' in /proc/vmallocinfo, and exclude them from /proc/kcore. Testing *** - I did basic testing on kvm guest, and run below commands to access kcore file to do statistics: makedumpfile --mem-usage /proc/kcore - Stephen helped to test v4 and confirm the problem he spotted and reported has been resolved with the v4 patchset. Changelog *** v4->v5: - Add a 'unlock' label and goto jumping in while loop of vmap_ram_vread() function, this improve the codes execution. This is done in patch 3. - Add Stephen's Reported-by and Tested-by tags in patch 3. v3->v4: - Fix typo in pach 2 catched by Lorenzo. - Add WARN_ON(flags == VMAP_BLOCK) in vread() to address Dan's concern that VMAP_BLOCK could be set alone in vmap->flags. - Add checking on the returned value from xa_load() in vmap_ram_vread(), Uladzislau commented on the risk of this place. - Fix a bug in s_show() which is changed in patch 5. The old change will cause 'va->vm is NULL but the VMAP_RAM flag is not set' case wrongly handled. Please see below link for details. - https://lore.kernel.org/all/Y8aAmuUY9OxrYlLm@kili/T/#u - Add Uladzislau and Lorenzo's Reviewed-by. v2->v3: - Benefited from find_unlink_vmap_area() introduced by Uladzislau, do not need to worry about the va->vm and va->flags reset during freeing. - Change to identify vm_map_area with VMAP_RAM in vmap->flags in vread(). - Rename the old vb_vread() to vmap_ram_vread(). - Handle two kinds of vm_map_area area reading in vmap_ram_vread() respectively. - Fix bug of the while loop code block in vmap_block reading, found by Lorenzo. - Improve conditional check related to vm_map_ram area, suggested by Lorenzo. v1->v2: - Change alloc_vmap_area() to pass in va_flags so that we can pass and set vmap_area->flags for vm_map_ram area. With this, no extra action need be added to acquire vmap_area_lock when doing the vmap_area->flags setting. Uladzislau reviewed v1 and pointed out the issue. - Improve vb_vread() to cover the case where reading is started from a dirty or free region. RFC->v1: - Add a new field flags in vmap_area to mark vm_map_ram area. It cold be risky reusing the vm union in vmap_area in RFC. I will consider reusing the union in vmap_area to save memory later. Now just take the simpler way to let's focus on resolving the main problem. - Add patch 4~7 for optimization. Baoquan He (7): mm/vmalloc.c: add used_map into vmap_block to track space of vmap_block mm/vmalloc.c: add flags to mark vm_map_ram area mm/vmalloc.c: allow vread() to read out vm_map_ram areas mm/vmalloc: explicitly identify vm_map_ram area when shown in /proc/vmcoreinfo mm/vmalloc: skip the uninitilized vmalloc areas powerpc: mm: add VM_IOREMAP flag to the vmalloc area sh: mm: set VM_IOREMAP flag to the vmalloc area arch/powerpc/kernel/pci_64.c | 2 +- arch/sh/kernel/cpu/sh4/sq.c | 2 +- include/linux/vmalloc.h | 1 + mm/vmalloc.c | 127 ++++++++++++++++++++++++++++++----- 4 files changed, 112 insertions(+), 20 deletions(-)